Inspection Procedure 7: The ASC OFF Display Remains Illuminated After the Engine Is Started

Inspection Procedure 7: The ASC OFF display remains illuminated after the engine is started.





CAUTION
^ Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
^ When the hydraulic unit (integrated with ASC-ECU) is replaced, always perform the calibration of steering wheel sensor, G and yaw rate sensor, brake fluid pressure sensor, cut valve, and inlet valve.

SYSTEM OPERATION
^ ASC-ECU sends the illumination request signal of ASC OFF display to the combination meter through ETACS-ECU via CAN communication.
^ By the operation of ASC OFF switch, the ASC OFF display illuminates when the ASC function is stopped.
^ When the ASC OFF switch is pressed shortly, the ASC system is turned OFF.

TECHNICAL DESCRIPTION (COMMENT)
In the case of this trouble symptom, there may be a short circuit to the ASC OFF switch circuit.

PROBABLE CAUSES
^ Damaged wiring harness and connectors
^ ASC OFF switch malfunction
^ ETACS-ECU malfunction
^ Combination meter malfunction
^ ASC-ECU malfunction

DIAGNOSIS

Required Special Tools:
^ MB991958 Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface (V.C.I.)
^ MB991827 M.U.T.-III USB Cable
^ MB991910 M.U.T.-III Main Harness

STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.
Using scan tool MB991958, diagnose the CAN bus lines.

Q: Is the check result normal?
YES: Go to Step 2.
NO: Repair the CAN bus lines. Then go to Step 9.

STEP 2. Scan tool diagnostic trouble code
Using scan tool, check the diagnostic trouble code for ASC system.

Q: Is any DTC set?
YES: Carry out the diagnosis for the DTC.
NO: Go to Step 3.

STEP 3. ASC OFF switch check

Q: Is the check result normal?
YES: Go to Step 4.
NO: Replace the ASC OFF switch Then go to Step 9.

STEP 4. Connector check: C-313 ETACS-ECU connector, C-42 intermediate connector, C-135 ASC OFF switch connector

Q: Is the check result normal?
YES: Go to Step 5.
NO: Repair the defective connector.

STEP 5. Wiring harness check between C-313 ETACS-ECU connector terminal No. 15 and C-135 ASC OFF switch connector terminal No.
^ Short circuit check of power supply circuit

Q: Is the check result normal?
YES: Go to Step 6.
NO: Repair the wiring harness between C-313 ETACS-ECU connector terminal No. 15 and C-119 ASC OFF switch connector terminal No. 1

STEP 6. Scan tool diagnostic trouble code for other systems
Using scan tool MB991958, check if diagnostic trouble code No. U0141 is set by the combination meter system.

Q: Is the DTC set?
YES: Diagnose the combination meter. Then go to Step 9.
NO: Go to Step 7.

STEP 7. Scan tool diagnostic trouble code for other systems
Using scan tool MB991958, check if diagnostic trouble code No. U0121 is set by ETACS system.

Q: Is the DTC set?
YES: Diagnose the ETACS-ECU. Then go to Step 8.
NO: Go to Step 8.

STEP 8. Retest the system.

Q: Does the ASC OFF display turn ON and OFF normally?
YES: Intermittent malfunction.
NO: Replace the hydraulic unit (incorporates in ASC-ECU). Then go to Step 9.

STEP 9. Retest the system.

Q: Does the ASC OFF display turn ON and OFF normally?
YES: The procedure is complete.
NO: Return to Step 1.